In conventional technology, coal is used to produce coal gas, natural gas, or used to produce gas by coking at high temperature, medium temperature or low temperature. However, the above-mentioned technology is required to form pulverized coal into lumps or sift lump coal, which increases the cost of raw material, or result in the produced gas without a high heat value, a big additional value, and significant economic and social benefits. The heating mode of furnace can be classified as external-heating mode, internal-heating mode and hybrid-heating mode. The heating medium in external-heating furnace is not contact directly with raw materials and heat is transferred from furnace wall. The heating medium in the internal-heating furnace contacts with the raw materials directly, and the heating methods are classified as solid heat carrier mode and gas heat carrier mode according to different heat mediums.
At present, there are two kinds of conventional coal decomposition apparatus, one of which has an up-draft kiln structure. The up-draft kiln structure is used for combusting flue gas and combustible gases produced by coal, which has low gas purity and a low additional value, as well as partially discharge of gas. This results in a significant resources wasting and environmental pollution. Another kind of coal decomposition equipment has a shaft kiln structure. In the structure, coal lumps are placed on clapboard with holes, and a heater is provided above the coal lumps. Because the coal lumps on the clapboard are accumulated to a certain thickness, so they cannot be uniformly heated and decomposed, and are required to be cyclically heated and decomposed by the decomposed gas. More importantly, since the presence of large amount of holes for ventilation and circulatory function provided on the clapboard, pulverized coal can leak through the holes. To avoid this, it is necessary to process the pulverized coal into coal briquette when introducing it into the shaft kiln. Thus, it will increase the cost of pulverized coal decomposition, and reduce the economic benefits because the pulverized coal cannot be directly used for coal decomposition in up-draft kiln.
There exists a coal material decomposition apparatus, which includes a closed kiln body with a feed inlet and a discharge outlet. A flame gas heating device is arranged in the kiln body. A propulsion and decomposition path of coal material is formed between the flame gas heating device and the inner wall of the kiln body. A coal decomposition gas collecting pipe which is communicated with the propulsion and decomposition path of coal material is arranged on the kiln body. In practice, this process using close-packed pipes is very complex, and heat transfer effect is poor in that heat is transferred mainly by thermal radiation. Additionally, the pipes for the propulsion of coal are also very complex when close-packed decomposition pipes are arranged in the kiln body and high-temperature heating bin is arranged outside the pipes. In this way, the propulsive mechanism and the pipes can also not be easily connected in a hermetical manner, which causes heat exchange to be inadequate.